Superconductive electro-magnetic device for use within a direct current motor or generator

ABSTRACT

A non-traditional topology of a superconductive electric motor or generator increases the air gap flux density by reducing stray flux and concentrating lines of flux within the air gap. An electric motor or generator utilizing the invention will include three components: a rotating armature, a permanent magnet stator and a shielding sleeve. The shielding sleeve of the motor is a hollow cylinder that fits between the armature and the stator, and is configured to cool a plurality of high-temperature superconductors within it to a temperature below their critical temperatures. These superconductors are placed at an optimized position to redirect flux and promote greater efficiency.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/882,790, filed Sep. 26, 2013, the contents of which are incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates generally to electric motors andgenerators that can be adapted for use in various systems orapparatuses. More specifically, the invention relates to anelectro-magnetic device for use with a direct current motor andgenerator that provides improved efficiency through the use ofsuperconductors.

BACKGROUND OF THE INVENTION

Electric motor construction that was developed in the 1800s uses a fixedplacement of magnetic fields to initiate an electromotive force (EMF).An increase of electrical current induces a larger or stronger magneticfield causing a greater electromotive force at a higher and lessefficient consumption rate. Therefore, a motor supplied with increasedelectrical current is limited to a particular RPM peak by a back EMF.

High temperature superconductors have been used to design electricmotors due to their high current density and low DC losses. Such motorsrequire cryogenic cooling systems to keep the temperature of thesuperconductors from rising too high.

A large portion of the electromagnetic energy lost by an electric motoris due to hysteresis and eddy currents. Hysteresis loss refers to theamount of electro-magnetic energy absorbed by ferrous metal when itsmagnetization is changed by the application of an alternating magneticfield. Eddy currents are currents unintentionally induced in conductivemotor components by the fields in the motor. These currents producemagnetic fields opposite of those that operate the motor, and thus actas a form of magnetic drag on the motor. Thus, there is a need for anelectric motor that decreases the energy losses due to these issues andprovides increased efficiency.

SUMMARY OF THE INVENTION

The invention relates to various exemplary embodiments, includingsystems and apparatus for electric motors and generators that provideincreased efficiency. These and other features and advantages of theinvention are described below with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view or a topology of an electro-magnetic devicein accordance with the invention.

FIG. 2 is a sectional view of a shielding sleeve as shown in FIG. 1.

FIG. 3 is a perspective view of the inner structure of the shieldingsleeve as shown in FIG. 2.

FIG. 4 is a perspective view of a shielding sleeve as shown in FIG. 1.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Before the present invention is described in further detail, it is to beunderstood that the invention is not limited to the particularembodiments described, and as such, may of course vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting, since the scope of the present invention will be limited onlyby the appended claims.

A number of materials are identified as suitable for various aspects ofthe invention. These materials are to be treated as exemplary and arenot intended to limit the scope of the claims. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present invention, a limitednumber of the exemplary methods and materials are described herein.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise.

The implementations of the present invention described herein are usedto increase the efficiency of a superconductive electric motor orgenerator by increasing its air gap flux density and decreasing lossesdue to hysteresis and eddy currents. In addition, the present inventionutilizes a large number of standard motor components, and therefore amotor or generator in accordance with the present invention caninterface with standard mechanical systems with minimal modification,and can be manufactured using standard and cost-effective processes. Itwill be understood that, as used herein, the term “motor” can also referto the inverse, a “generator” and vice versa.

In the event that a rotational force is applied to the shaft of theinvention, it will act as a generator, supplying power to any loadconnected to the terminals. The same properties of the invention thatwould increase its efficiency as a motor will also increase itsefficiency as a generator. The invention will result in an increasedefficiency, whether used as a motor or generator regardless of itsprimary application. The reverse conversion of mechanical energy intoelectrical energy is done by a generator. Motors and generators havemany similarities, and many existing motors can be driven to generateelectricity.

Exemplary embodiments of the present invention might significantlyincrease the available driving range of a battery pack in a vehicle andmake non-hybridized electric vehicles viable to everyday commuters. As aresult, it might facilitate a viable transition from gasoline propulsionvehicles to electric, non-hybridized vehicles.

As shown in FIG. 1, an electro-magnetic device 1 in accordance with anembodiment of the present invention includes a rotating armature 10, apermanent magnet stator 20, and a shielding sleeve 30. The rotatingarmature 10 is shown at the center of the motor 1 and associated withbearings and a brush assembly (not shown).

The shielding sleeve 30 is a hollow cylinder that fits between thearmature 10 and the stator 20. The shielding sleeve 30 is configured tocool a plurality of high-temperature superconductors 40 located withinthe sleeve 30 to a temperature below the critical temperature of thesuperconductors 40. High-temperature superconductors 40 with criticaltemperatures of about 100K, can be cooled by a fairly simplecryo-cooler, or alternatively by liquid nitrogen (LN2), which has aboiling-point of 77.4 K. There are two principal high-temperaturesuperconducting materials: Yttrium-Barium-Copper-Oxide (YBa2Cu3O7, orYBCO), and Bismuth-Strontium-Calcium-Copper-Oxide (BSCCO). In oneexemplary embodiment of the present invention, the device 1 uses YBCO toinduce a diamagnetic repulsion field. YBCO exhibits the highest currentdensity. Its critical temperature is around 90K allowing its use atliquid nitrogen temperature. At 77K, this material can trap about 1.3Tesla (T) of magnetic flux and more than 6 T below 50K.

Referring to FIG. 2, the inner core of the sleeve 30 is formed of anurethane foam, such as about 1″ thick insulated hollow cylinder 100 of 3lb/ft³ urethane foam. The cylinder 100 is encased in a fiberglasshousing formed of resin that is capable of withstanding cryogenictemperatures. The fiberglass enclosure is mandrel wound to a thicknessof about 3/16″. Insulated end caps 110 of similar composition areattached to the ends of the central cylinder 100. These end caps 110have an inner diameter of about 6″ and an outer diameter of about 10″.LN₂ can be introduced within the cylinder 100 to provide cooling for thesuperconductors. One of these end caps 110 has a nitrogen introductionport that is fitted to receive the phase separator of a bulk liquidnitrogen tank. The other end cap 110 has a gas port that allowsevaporated nitrogen to escape from the sleeve 30.

Referring to FIGS. 3 and 4, a plurality YBCO 123 superconductive bulkplates 40 are mounted to the outer surface of the hollow cylinder 100,between the end caps 110. The superconductive bulk plates 40 each havedimensions of about of 3″×1½″×½″. The bulk plates 40 are arranged infour sets, each of which has overall dimensions of about 3″×6″×½″. Eachset of bulk plates 40 covers an arc of approximately 45°. As shown inFIG. 4, all four sets of bulk plates 40 are uniformly distributed aroundthe cylinder 100 so that there is also an arc of approximately 45°between them, i.e., the gap is also about 45°. While this arrangementprovides optimal results, other arc and gap measurements are also withinthe scope of the present invention. Additional bulk fiberglass (notshown) can be inserted beneath each bulk plate 40 in order to provide aflat contact surface and prevent cracking of the plates. The bulk plates40 are held in place by a fiberglass enclosure 120 adhered to the innercylinder 100, which is perforated to allow greater thermal contactbetween liquid nitrogen in the sleeve 30 and the bulk plates 40.

Referring to FIGS. 2 and 4, surrounding the inner cylinder 100 of thesleeve 30, there is a hollow cylinder 130 made of fiberglass. Thecylinder 130 has an outer diameter of about 10″ and a thickness of about3/16″. It slides over the end caps 110 and seals against them, formingthe outer wall 140 of the sleeve 30. A void is enclosed between theinner cylinder 100 and the outer wall 140, and is sealed on the ends bythe end caps 110. This void contains the bulk plates 40, and also servesas a nitrogen bath to cool the bulk plates 40 to their criticaltemperature. LN₂ can be introduced into this void space to provide thenecessary cooling.

The permanent magnet stator 20 illustrated in FIG. 1 is designed toaccommodate the sleeve 30. In this implementation, it is designed as anoctagon made of aluminum bar stock having dimensions of about 5″×½″×14″long. Each end of stator housing 60 is enclosed with a ½″ thickoctagonal aluminum end plate. Rare earth magnets 50 having dimensions ofabout 1″×3″×6″ are attached to the housing 60 at 90° intervals. Themagnets 50 are affixed with alternate poles facing inward, so that likepoles face each other across the main axis of the device 1. Other typesof magnets—conventional, rare earth, electromagnet, even superconductivewindings—could also be used according to the present invention.Variation in the types of magnets used would cause a variation in theshapes and geometries of the magnetic fields. The optimal shielded arcwould vary with magnet type, composition, and geometry.

The stator housing 60 can be constructed in two halves with the endplates being attached to the lower half. This permits access to thesleeve 30. Flanges are welded to the halves, allowing them to be boltedtogether.

All void space between the stator housing 60 and the sleeve 30 is filledwith 3 lb/ft³ urethane foam. The foam insulates the outer wall 140 ofthe sleeve 30 from the housing 60, and thus reduces the heat load on thenitrogen bath. It also provides a friction fit on the sleeve 30 bylocking it in place when the stator flange bolts are tightened.

Prior to operating the device 1 with a motor or generator, the sleeve 30is rotated manually within the stator 20 so that each set of bulk plates40 is aligned between the stator poles. Liquid nitrogen is thenintroduced into the sleeve 30 to cool the bulk plates 40 to theircritical temperature. Once the bulk plates 40 reach their criticaltemperature, the magnetic flux generated by the stator magnets 50 istrapped inside the bulk plates 40. The sleeve 30 is then rotated 90° sothat the trapped flux is opposite in polarity to the magnet nearest toit. At this point the device 1 is operational.

These bulk plates 40 are flooded with low pressure liquid nitrogen andthe cryo-unit holds them at an optimized position in front of fourneodymium magnets 50. These fields generated are above an armature thatgenerates a field for EMF. Other magnets can be used within the scope ofthe invention as may be desired.

The implementation described utilizes liquid nitrogen to cool andinsulate the superconductors. Other implementations could utilizeconductive cooling or other types of cooling mechanisms known to thosewith skill in the art. If thermal conduction is used to cool thesuperconductors, the sleeve would be formed of a thermally conductivematerial.

This design increases the efficiency of the motor or generator byreducing stray flux. The activated bulk plates 40 increase the air gapflux density and concentrate the lines of flux between them. This fluxis in the optimum area to interact with the armature fields and producepositive torque. The reversed polarity of the flux trapped in the bulkplates 40 cancels flux from the stator fields near the edges of theplates, leaving only the concentrated field between the plates tointeract with the armature. In the reverse direction, the armaturefields are likewise concentrated by the bulk plates 40 and focused onthe stator magnets 50. As a result, losses due to hysteresis currentsand eddy currents are reduced.

EXAMPLE

A 1 horsepower motor was mounted on a test stand so that it would drivea belt and pulley system, driving the prototype as a generator accordingto the invention. A power meter was connected to the power supply of thedrive motor to measure the input power. The leads of the device wereconnected to a 45 watt light bulb within the circuit path. The currentproduced by the prototype motor was measured using an ExTech MA220ammeter; the voltage produced was captured using a Snap-On M.O.D.I.S.running 12.2 software. By varying the combination of pulleys used toconnect the two machines, the motor could be driven at one of fourspeeds: 3510, 2995, 2630, and 1910 rpm.

The testing began with what is referred to as the conventional motortest. This test consisted of running the motor up to speed withoutactivating the superconductive bulk plates and recording the powerconsumed by the drive motor and the light bulb. This test was run tentimes at all four speeds. After this test was run, the sleeve was set inone of two positions (+5 or −5) and activated. In these positions, thebulk plates are aligned radially between the stator field magnets. Thetwo positions are 90 degrees apart, so the only difference between themis which superconductor is aligned between each pair of stator magnets.Ten tests were then run at each speed. After these tests were run, thesleeve was rotated 90 degrees to the opposite position (+5 or −5) andten more tests would be run at each speed. This resulted in tests beingrun with the sleeve activated at +5 and operated at +5 and −5, and withthe sleeve being activated at −5 and run at −5 and +5. In total, 16series of ten tests were run; one at each speed for each possiblecombination activation and operation points. The data are shown below.

% Increase In Efficiency Over Conventional Motor Speed (rpm) +5, +5 +5,−5 −5, −5 −5, +5 3510 22.12% 25.75% 29.92% 30.73% 2995 −2.35% 8.27%11.51% 5.92% 2630 10.04% 10.06% 8.72% 12.51% 1910 9.40% 15.91% 15.74%24.19%

The results of these tests are clear. 15 of the 16 test series showedstatistically significant increases in efficiency over the non-activatedmotor with an average increase of 14.9% efficiency above thenon-activated invention operating at the same speed. As noted above,this test was intended to prove the concept of the invention. It did notprovide an exact estimate of how much the invention will increase theefficiency of a DC motor operating in its intended use. The efficiencyof the device did increase when the sleeve was activated, proving thatit did produce a significant reduction in stray loads (hysteresis andeddy currents). The invention will have the same effect on a motor, butthe magnitude of the reduction in stray loads will be affected by thegeometry of the motor and its magnetic fields.

Numeric values and ranges are provided for various aspects of theimplementations described above. These values and ranges are to betreated as examples only and are not intended to limit the scope of theclaims.

While the invention has been described in conjunction with specificexemplary implementations, it is evident to those skilled in the artthat many alternatives, modifications, and variations will be apparentin light of the foregoing description. Accordingly, the invention isintended to embrace all such alternatives, modifications, and variationsthat fall within the scope and spirit of the appended claims.

What is claimed is:
 1. A superconductive electro-magnetic device for usewithin a direct current motor or generator that includes an armaturethat rotates when a rotational force is applied thereto and a permanentmagnet stator within which the armature rotates, the device comprising:a hollow shielding sleeve located between the armature and the stator,the shielding sleeve having an inner wall and an outer wall, such that acooling fluid can flow within the shielding sleeve; and a plurality ofsuperconductor plates located between the inner wall and the outer wallof the shielding sleeve and oriented around the armature, and at leastone of the following: wherein the hollow shielding sleeve includes aninner core formed of urethane foam, or wherein the superconductor platesare attached to the inner wall of the shielding sleeve and are arrangedat intervals of about 45° around the shielding sleeve, or wherein thesuperconductor plates are attached to the inner wall of the shieldingsleeve and bulk fiberglass provides a flat contact surface between thesuperconductor plates and the shielding sleeve.
 2. The device of claim1, wherein the cooling fluid is liquid nitrogen.
 3. The device of claim1, wherein the superconductor plates are formed ofyttrium-barium-copper-oxide or bismuth-strontium-calcium-copper-oxide.4. The device of claim 1, wherein the shielding sleeve includes an innercore formed of urethane foam.
 5. The device of claim 4, wherein theinner core is encased in a fiberglass housing.
 6. The device of claim 1,wherein the inner core includes insulated end caps.
 7. The device ofclaim 1, wherein the superconductor plates are attached to the innerwall of the shielding sleeve.
 8. The device of claim 7, wherein thesuperconductor plates are arranged at intervals of about 45° around theshielding sleeve.
 9. The device of claim 7, wherein bulk fiberglassprovides a flat contact surface between the superconductor plates andthe shielding sleeve.
 10. The device of claim 1, wherein the statorincludes rare earth magnets attached to a housing located at each end ofthe stator.
 11. The device of claim 10, wherein the magnets areneodymium magnets.
 12. A superconductive electro-magnetic device for usewithin a direct current motor or generator that includes an armaturethat rotates when a rotational force is applied thereto and a permanentmagnet stator within which the armature rotates, the device comprising:a hollow shielding sleeve located between the armature and the stator,the shielding sleeve formed of a thermally conductive material; and aplurality of superconductor plates located within the shielding sleeveand oriented around the armature, and at least one of the following:wherein the hollow shielding sleeve includes an inner core formed ofurethane foam, or wherein the shielding sleeve includes an inner walland the superconductor plates are attached to the inner wall of theshielding sleeve and are arranged at intervals of about 45° around theshielding sleeve, or wherein the shielding sleeve includes an inner walland the superconductor plates are attached to the inner wall of theshielding sleeve and bulk fiberglass provides a flat contact surfacebetween the superconductor plates and the shielding sleeve.
 13. Thedevice of claim 12, wherein the shielding sleeve includes an inner walland an outer wall, such that a cooling fluid flows within the shieldingsleeve and the superconductor plates are located between the inner walland the outer wall.
 14. The device of claim 13, wherein thesuperconductor plates are attached to the inner wall of the shieldingsleeve.
 15. The device of claim 14, wherein the superconductor platesare arranged at intervals of about 45° around the shielding sleeve. 16.The device of claim 14, wherein bulk fiberglass provides a flat contactsurface between the superconductor plates and the shielding sleeve. 17.The device of claim 12, wherein the superconductor plates are formed ofyttrium-barium-copper-oxide or bismuth-strontium-calcium-copper-oxide.18. The device of claim 12, wherein the shielding sleeve includes aninner core formed of urethane foam.
 19. The device of claim 18, whereinthe inner core is encased in a fiberglass housing.
 20. A superconductiveelectro-magnetic device for use within a direct current motor orgenerator that includes an armature that rotates when a rotational forceis applied thereto and a permanent magnet stator within which thearmature rotates, the stator including rare earth magnets attached to ahousing located at each end of the stator, the device comprising: ahollow shielding sleeve located between the armature and the stator, theshielding sleeve having an inner wall and an outer wall and having aninner core between the inner wall and the outer wall, the inner coreformed of urethane foam encased in a fiberglass housing, such that aliquid nitrogen cooling fluid can flow within the shielding sleeve; anda plurality of superconductor plates attached to the inner wall of theshielding sleeve and oriented around the armature at intervals of about45° around the shielding sleeve.